This invention relates generally to a thermal exchange composition and more particularly to a heat or cold retaining composition which can be incorporated into many articles including hot and cold packs, toys, seat cushions, or food trays.
Many different compositions and devices for heating or cooling surfaces or objects have been tried and used in the past in a limitless variety of applications. Particularly, many heating or cooling devices have been applied to the human body for therapeutic treatment. For instance, hot water bottles and ice packs still remain as very popular articles for application to sore areas of the body.
Recently, other heat or cold retaining compositions have been developed. These compositions are capable of absorbing, storing, and then releasing heat or cold over an extended period of time. For example, a PCT application, International Publication No. WO90/05508, to Wilkins discloses a heating pad comprising a heat retaining base material formed from gel, wax or oil, within a sealed flexible container. Heat storage mediums such as fibers, threads, or foam particles can be interspersed within the base material. Other additives could include polyurethane foam or china clay, which is also known as kaolin.
U.S. Pat. No. 4,253,983 to Blanie discloses a paraffin composition that can be used as a shapable heat casing constituent. The paraffin composition can contain finally divided metals, their oxides, or their silicates. Additionally, kaolin can be added.
U.S. Pat. Nos. 4,743,726 and 4,849,593, which were jointly invented by one of the present inventors, also disclose heat exchange mediums. The heat exchange medium in the '726 patent includes a microwave heatable outer structure made of a heat and flame resistant rubber coated with a high temperature lubricant assembled together with a water impregnable cellular core saturated with water. The whole assembly has at the longitudinal and diametrical center a wax core with a high melting point. The patent discloses a number of applications for the heat exchange medium, such as hair rollers, curling irons, food warmers, and heating pads.
The '593 patent discloses another microwave activated heating element made from a variety of compositions. In one particular form, a cartridge includes a core of wax material, a layer of open cellular water retaining material, a layer of rubber, and an outer layer of paper. In another embodiment, the cartridge consists of a central core formed of a wood dowel, an annular overlay of rubber material with an appropriate high temperature lubricant disposed therebetween, and an outer covering, for example, formed of paper. Another form disclosed in the '593 patent includes a heating element comprising clay, which can be mixed with water and oils. The mixture may also include rubber particles and a high temperature lubricant.
A soft, light weight toy for a child having an animal-like appearance and including a removable bladder filled with a heat transfer liquid is disclosed in U.S. Pat. No. 4,714,445 to Templeton. Suggested materials to fill the bladder and act as a heat reservoir include water, aqueous solutions, glycerol, mineral oils, and various other viscous fluids or gels. The fluid can be heated or cooled and the bladder can be inserted into the toy for making the toy warm or cool to the touch.
Soviet Union Patent No. 1452-833-A further discloses a composition made from crushed powdered clay and a dust or oil for protecting foundations against frost effects.
Although the prior art discloses an assortment of heat exchange mediums and corresponding applications for those mediums, the particular composition of the present invention remains absent. Further, the prior art has its drawbacks and deficiencies. For instance, some of the prior art compositions contain materials considered to be toxic or generally unsafe. Consequently, disposal of these items raises a number of environmental issues. Also, some of the prior art devices contain low viscous liquids. If the containment pouch were ruptured during use, these liquids would flow out of the container and possibly burn the user. Further, some of the prior art mediums simply do not meet the thermal requirements of some applications. The present invention overcomes the shortcomings of the prior art in that a thermal exchange composition is disclosed that effectively absorbs, stores, and releases higher and lower temperatures.
A PCT application, International Publication No. WO92/20755, directed to a heat exchange medium was filed by one of the current inventors. The particular features of the present invention, however, remain absent from the published PCT application as will be apparent to one skilled in art from the detailed description which follows. That application is incorporated herein in its entirety by reference thereto.